It is known that bubbles with a small diameter have various physiological functions. Nowadays, much attention is paid to a technique for producing such bubbles and to effects exerted by such bubbles.
Such bubbles are classified into micro bubbles, micro-nano bubbles, and nano bubbles, according to their diameter. Specifically, micro bubbles have a diameter ranging from 10 μm to several ten μm at a time they are produced, micro-nano bubbles have a diameter ranging from several hundred nm to 10 μm at a time they are produced, and nano bubbles have a diameter of not more than several hundred nm at a time they are produced. Micro bubbles may be partially converted into micro-nano bubbles due to contraction after they are produced.
Studies of micro bubbles have advanced greatly, and various physiological functions of micro bubbles have been discovered. For example, Non-Patent Document 1 (Hitoshi Okajima, “Application of micro bubbles to medical treatment and its possibilities”, Clean Technology, 2007, Vol. 17, No. 1) describes physiological functions of micro bubbles: (1) function for promoting growth of oysters and scallops; (2) function for promoting production of an insulin-like growth factor-1; and (3) function for increasing blood flow.
Furthermore, Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-321959 (Tokukai 2004-321959; published on Nov. 18, 2004)) describes that a waste-liquid treatment device using micro bubbles made of ozone gas (ozone micro bubbles) has been conventionally used. The waste-liquid treatment device produces micro bubbles made of ozone gas, by mixing ozone gas from an ozone-producing device and a waste liquid with use of a pressure pump. The micro bubbles chemically react with organic matters in the waste liquid, so that the organic matters in the waste liquid are oxidized and decomposed.
Furthermore, Patent Document 2 (Japanese Unexamined Patent Publication No. 2006-320675 (Tokukai 2006-320675; published on Nov. 30, 2006)) describes that a method and a device for producing micro bubbles made of carbon dioxide (carbonic gas micro bubbles) have been conventionally used. Patent Document 2 describes that the micro bubbles made of carbon dioxide can be produced by providing a carbonic gas container and a pressure-reducing valve in an air-introducing system of a micro bubble-producing device and supplying carbonic gas to the air-introducing system with a certain pressure and certain flow volume. Efficiency in solution of carbonic gas is nearly 100% of theoretical efficiency, and therefore only a small amount of carbonic gas is required, which is economic. Furthermore, Patent Document 2 describes that the device is compact.
However, the above micro bubble techniques have a problem that the techniques cannot fully make use of physiological functions of micro bubbles. For example, only a small amount of the carbonic gas micro bubbles is absorbed via skin, resulting in that the function for promoting production of an insulin-like growth factor-1 and the function for increasing blood flow are not fully performed. For that reason, nowadays, much attention is paid to nano bubbles that have further smaller diameter than that of micro bubbles, and to a device and a method for producing the nano bubbles.
For example, Patent Document 3 (Japanese Unexamined Patent Publication No. 2003-334548 (Tokukai 2003-334548; published on Nov. 25, 2003)) describes that a method for producing nano bubbles from a liquid as a raw material has been conventionally used. The method includes a step (1) of, in a liquid, decomposing and gasifying a part of the liquid, a step (2) of, in a liquid, applying supersonic waves to the liquid, or a step (3) of, in a liquid, decomposing and gasifying a part of the liquid and applying supersonic waves to the liquid. It is described that the step of decomposing and gasifying a part of the liquid may be carried out through electrolysis or photolysis.
Furthermore, Patent Document 4 (Japanese Unexamined Patent Publication No. 2004-121962 (Tokukai 2004-121962; published on Apr. 22, 2004)) describes that a method for using nano bubbles and various devices using nano bubbles have been conventionally used. More specifically, Patent Document 4 describes that nano bubbles reduce a buoyant force, increase a surface area, increase surface activity, produce a local high pressure area, or realize electrostatic polarization, thereby performing surface-active function and fungicidal action. Furthermore, Patent Document 4 describes a technique for cleaning various objects and polluted water by using the surface-active function and the fungicidal action of nano bubbles. Furthermore, Patent Document 4 describes a method for curing fatigue of a living body with use of nano bubbles. Furthermore, Patent Document 4 describes production of nano bubbles by electrolyzing water and applying supersonic wave vibration to the water.
However, the conventional devices and methods for producing nano bubbles cannot produce a large amount of carbonic gas nano bubbles and therefore the devices and the methods cannot fully make use of physiological functions of carbonic gas nano bubbles (e.g. function for increasing blood flow and function for promoting production of insulin-like growth factor-1).
It has been widely known that carbonic gas included in a carbonate spring increases blood flow. Hot springs where concentration of carbonic gas in a carbonate spring is approximately 1000 ppm exist in Europe (e.g. Germany), and such hot springs are used for various medical treatments. In contrast, hot springs where concentration of carbonic gas in a carbonate spring is approximately 1000 ppm do not exist in Japan. Therefore, for medical treatment, it is necessary to produce carbonic gas nano bubbles of 1000 ppm or more in carbonic gas concentration. However, the conventional devices and methods for producing nano bubbles cannot produce carbonic gas nano bubbles of 1000 ppm or more in carbonic gas concentration.
It is deemed that carbonic gas nano bubbles exert their effects on a human body greatly at a time when the diameter of each carbonic gas nano bubble is not more than 1 μm and is approximately several ten nm. However, the conventional devices and methods for producing nano bubbles cannot produce a large amount of carbonic gas nano bubbles with so small a diameter as to exert full effects on a human body.
Furthermore, the conventional devices and methods for producing nano bubbles have a problem that, after a medicinal component derived from a galenical or a moisture-retaining component derived from a moisture-retaining agent is dissolved in bath water, the medicinal component or the moisture-retaining component cannot be efficiently absorbed in a living body concurrently with absorption of carbonic gas nano bubbles.